Shockpkoof electromagnetic



Nov. 30, 1948.

P. G. EDWARDS ETAL SHOCK-PROOF ELECTROMAGNETIC CIRCUITCONTROLLER Filedlarch 15, 1944 F/GI R a. EDWARDS c; HWHERR/NGTOV W BY r 4 a 14% 82 M1-A77URNEV Patented Nov. 30, 1948 SHOCKPROOF ELECTROMAGNETIC CIRCUIT CONTROLLEB.

Paul G. Edwards and Harold W. Harrington, Verona, N. 1., asslgnors toBell Telephone Laboratories, Incorporated poration of New York New York,N. Y., a cor- Application March 15, 1944, Serial No. 526,530

4 Claims. (01. 200-37) This invention relates to electric circuitcontrollers and particularly to switching devices of the type thatfunction to control electric circuits through the media ofarmature-operated contact springs.

In general, circuit controllers function to complete, or to interrupt acircuit by causing a contact bearing spring to be moved, under theaction of an armature, into or out of engagement with an associatedstationary contact included in the circuit to be controlled. Frequently,such devices are used under conditions which expose them to shock, whichproduces armature vibration and spring deflections and thereby causesthe false and untimely operation of the controlled circuits.

It is the object of this invention to provide a circuit controller, orswitching device which precludes the possibility of false and untimelycircuit operation under conditions of shock.

This object is attained, in a switching device, by the use of duplicatecircuit controlling contact springs mounted on diagonally disposed upperand lower faces of a dynamically balanced armature which is mounted forrotation about its center transverse axis. More particularly, thearmature is balanced for rotation about its transverse center line sothat any forces, produced by shock or impact, which act upon thearmature at one side of its pivot support and tend to produce rotationof the armature in one direction are counterbalanced by similar forceswhich act upon the armature at the other side of its pivot support andtend to rotate the armature in the opposite direction. The armatureaccordingly, is rendered unresponsive to such forces and maintains itsnormal stable condition when subjected to shock. By virtue of themounting of duplicate contact springs on upper and lower j diagonallydisposed faces of the armature, it is necessary for both springs to bejointly moved into. or out of engagement with their correspondingstationary contacts in order for a switching func tion to be performed.When such springs flex in response to shock or impact, to which thecontroller is subjected, they do so in such a manner that one flexes ina direction which tends to separate the spring from its stationarycontact, while the other flexes in a direction which tends to emphasizeits engagement with its corresponding stationary contact, therebyprecluding the joint operation of the springs in such directions aswould cause the completion of a switching operation.

The invention will be readily understood from the following detaileddescription when read in connection with the accompanying drawings, inwhich:

Figs. 1, 2 and 3 are top plan, end, and side elevations, respectively,of an electromagnetic switching device embodying the features Of theinvention in one of its aspects. It is to be understood that theparticular form of magnetic circuit illustrated in these figures hasbeen chosen for illustrative purposes only, and that any other suitableform of magnetic structure may be employed;

Fig. 4 is a detail assembly of the contact springs and armatureincorporated in the switchin device of Figs. 1, 2 and 3 and illustratesthe manner in which the springs are mounted on the armature and in whichthey may be electrically interconnected if required;

Figs.'5, 6, 7, 8, 9 and 10 are schematic configurations which illustratethe invention in its application to various types of contact control,such as single and double pole series, or make contacts; single andmultiple break contacts; and

transfer contacts. Each of these figures will be described individuallyhereinafter.

The electromagnetic structure elected for illustrative purpose and shownin Figs. 1, 2 and 3 consists essentially of a horizontally disposed coilI!) mounted on a magnetic core l2, and two L- shaped pole-pieces I3 andI4, each of which has a vertically extending portion abutting adifferent end of the core 12 and a horizontal inwardly projectingportion. The vertical portions of the pole-pieces are of diflerentlengths so that their respective horizontal portions project inwardly indiiferent parallel planes, the horizontal por tion of pole-piece l3being at a higher level than that of the horizontal portion ofpole-piece l4.

An insulating base l5 has secured thereto, by means of bolts I 8, twobrackets l1 and it of nonmagnetic material. The bracket l'! may beriveted or otherwise fixed to the lower end of the vertical portion ofpole-piece l2. Riveting of these two members is indicated at IS in Fig.2. The bracket I 8 is provided with a relatively long vertical portionwhich serves as a guide and support for a cover whose location isindicated by the broken lines in Fig. 3. Near its lower end this portionof bracket I8 is centrally apertured to receive a screw 20 which passesthrough a corresponding hole in the vertical leg of pole-piece l3 andscrews into a tapped, or threaded hole in the left end of core l2. Thebase l5 carries several terminals 2| by virtue of which various externalcircuit connections may be made to E coil 2| and to the stationarycontacts of the switching device.

A pair of brackets 22, 23 interconnect the inwardly projecting end ofthe horizontal portions of pole-pieces I3 and I4 and each consists oftwo short horizontal legs interconnected by a diagonal bridge piece. Theupper horizontal legs of both brackets are spot Welded, or otherwisefixed to the upper surface of the horizontal projection of polepiece l3,while the lower horizontal legs of both brackets are similarly securedto the under surface of the horizontal projection of pole-piece I4. Thediagonal pieces of the brackets 22, 23 are provided with centrallylocated aligned holes which receive a pin 24 which passes through thearmature 25 at its center transverse axis and constitutes a supportabout which the armature is rotated. I

As hereinbefore indicated, the armature 25 is mounted on its pivot pin24 in such amanner that it is in a condition of stable equilibrium. As

more clearly shown in Fig. 4, the armature 25 carries on its upper andlower faces identical spring pile-ups, each consisting of a fiatinsulator 28, a reinforcing flat metal sheet 29 and a pair of contactsprings 30 and 3|. The elements j t identified are arranged in the ordernamed in superposed relation, with the insulator 28 supported directlyon the armature. A pair of rivets 32 serves to support both springpile-ups on the armature and to electrically inter-connect the springsmounted on the upper face of the armature with those mounted on thelower face of the armature if the requirements of the circuit in whichthe controller is used necessitate such interconnection. It will beunderstood that the elements of one spring pile-up are identical to thecorresponding elements of the other spring pileup and that both springpile-ups contain the same number of elements. Further, each springpileup is located on its respective armature surface in the sameposition relative to the center transverse axis of the armature so thatthe balanced condition of the armature is not disturbed. As clearlyshown in Fig. 1, contact springs 30 and 3| are of the parallel contacttype which provides double assurance against faulty contact.

The bracket 22 is provided with an integrally formed hook-lineprojection 35 which serves as an armature back stop. A spring 36 servesto restore the armature to normal position against back stop 35. Thisspring 36 is fixed at one end to a lateral projection 31 on the bracket23 while its other end is hooked to fit under the armature as shown inFig. 3 and does not disturb the balanced condition of the armature.

The stationary contacts which engage with the contacts carried by thesprings are insulatively mounted on the horizontal portions of thepolepieces l3 and I4. Those stationary contacts which function with thesprings mounted on the upper surface of the armature 25 are supported onthe upper surface of the horizontal portion of pole-piece 14, whereasthose which function with the springs mounted on the lower surface ofthe armature are supported on the lower surface of the horizontalportion of pole-piece 13. As shown in the drawing, the upper and lowerstationary contact elements are insulatively separated from each otherby collars 38 through which screws 39 pass in securing the contactelements in position on the pole-piece.

When the coil I0 is energized the balanced armature 25 is rotated in aclockwise direction about its pivot 24 and carries with it the C ntactsprings supported on its upper and lower surfaces causing them tosimultaneously engage with, or disengage from their correspondingstationary contacts.

Fig. 5 is a schematic illustration of a balanced armature 25 which, whenoperated, causes the simultaneous closure of the duplicate contacts 42.The small full arrow indicates the direction of armature rotationresulting from the energization of a coil such as the coil ill. Thecontacts illustrated are of the make type and, as is obvious, bothcontacts must be closed to effect a switching function.

If it is assumed that the switching device having the armature andcontact arrangement schematically shown in Fig. 5 is dropped, orotherwise subjected to shock such as to cause the application of forcesto the armature in a direction indicated by the broken line arrows, thearmature will maintain its normal position. This is due to the fact thatthe moments of the forces acting upon the armature at each side of itspivot support will counterbalance each other, it being understood thatthe armature by design, is normally balanced. The contact spring 50carried on the upper surface of the armature will, however, respond tothe shock or impact and will flex in a direction such that it may engagethe righthand stationary contact 42. Contact spring 5|, however, willflex in the same direction and tend to move further away from itsassociated lefthand stationary contact 42 with the over-all result thatthe normal open condition of the controlled circuit is maintained.Should the shock, or impact to which the switching device is subjectedcause flexing of the springs in the opposite direction the contactspring 5| may flex so as to engage its corresponding contact 42 but thecon? tact spring 50 will flex in a direction such as to emphasize theopen condition at its corresponding contact 42. The normal opencondition of the circuit will thus be maintained and the possibility offalse circuit operation resulting from shock is precluded. While singlecontacts are indicated in Fig. 5 it will be understood that parallelcontacts of the type shown in Fig. 1 may be employed.

Fig. 6 distinguishes from Fig. 5 only in that it shows a double polearrangement suitable for use in cases requiring the control of more thanone circuit.

In Fig. 7 duplicate sets of multiple contacts are shown normallybridging the controlled circuit through their respective contactsprings. These contacts are break contacts and normally provide twoparallel closures of the controlled circuit. As in the case of Figs. 5and 6, it is necessary that both contact sets be opened to effect thecompletion of a switching function, that is, to'

effectively open the controlled circuit. As described in connection withFig. 5, the balanced armature 25 of Fig. 7 is immune to shock. Also, anyforce to which the switching device is subjected and which causes thecontact springs to flex will cause spring 53 to flex in a direction awayfrom its corresponding stationary contacts 54 and cause one of thenormal closures of the controlled circuit to be opened. The contactspring 55, however, will tend to flex in a direction towards itscorresponding stationary contacts 56 and thereby will emphasize thecircuit closure at these contacts. The normally closed condition of thecontrolled circuit accordingly, is not disturbed when the switchingdevice is subjected to shock. Obviously, any forces of shock which tendto cause spring 55 to move out of engagement with the stationarycontacts '56 will tend to emphasize the engagement of spring 53 with itscontacts 54 and thereby maintain the controlled circuit in its normalclosed condition.

Fig. 8' illustrates a transfer arrangement in which the battery 60 isnormally connected to the lead B by way of the duplicate sets ofmultiple contacts 6|, 62 and their corresponding contact springs 63 and64, respectively. The lead C to which the battery 60 is transferred whenthe controller is operated is normally open-circuited at contacts 65,which contacts are serially connected with contacts 66, when thecontroller is operated, by way of springs 61 and 68. When the armature25 is rotated in the direction indicated by the arrow the springs 63 and84 are moved out of engagement with their respective contacts 6| and 62and thus disconnect the battery 60 from lead B. Springs 61 and 68 aremoved into engagement with their respective contacts 65 and 56 thusconnecting the battery 60 to the lead C.

Should the controller equipped with the contact arrangement shown inFig. 8 be dropped or otherwise subjected to shock such as to cause theapplication of forces to the armature in a direction indicated by thebroken arrow, the armature 25, due to its balanced condition willmaintain its normal position. Springs 63, 64, 61 and '38 will all tendto flex in the same direction. Spring 63 may move out of engagement withits contacts Bl but spring 64 will tend to emphasize s engagement withsprings 62 so that the normal connection of battery to lead B ismaintained. Similarly spring 6'! may flex so as to move into engagementwith contacts 65 but spring 68 will separate further from contacts 66 sothat no transfer operation occurs. Should the controller be subjected toshock or impact such as to cause the application of forces to thearmature 25 in a direction opposite to that indicated by the brokenarrow the normal con nected condition of the battery to lead B will bemaintained at contacts SI and spring 63 and though spring 68 may engagecontacts 66, t lead C will be held open at contacts 65.

In cases where it is desirable to effect a transfer operation only whenthe controller is released, it is essential that the device beshockproof when in its operated position. Such a condition is met by thearrangement illustrated in Fig. 9 where the armature 25 is shownoperated. Under this operate condition the connection from battery 60 tolead B is effected by the duplicate sets of contacts H and 72 and theirassoc ated contact spirngs l3 and M, while the lead C is opened atcontacts wh ch are serially connected to the battery 60 by way of spring16, contacts 11 and spring 18 when the controller is released. It isapparent that when the controller is deenergized and the armaturerotates in a counter-clockwise direction, springs 13 and 14 move out ofengagement with their assoc ated stationary contacts H and 12 andthereby disconnect battery 60 from lead B, while springs 16 and 18 moveinto engagement with their respective stationary contacts 15 and H toconnect battery so to the lead C to complete the transfer operation.

Should the controller schematically shown in Fig. 9, when in itsoperated position, be sub ected to shock or impact such as to cause theapplication of forces thereto in a direction indicated by the brokenarrow, spring '14 may flex so as to move out of engagement with itscontacts 12 but the spring 13 would tend to flex in the same directionand thereby maintain the connection of battery to the lead B by way ofcontacts 1 l. Similarly, though spring 18 might flex so as to engagecontacts 11, the lead C would still be open at contacts 15 since springI6 would flex in a direction such as to increase its separation fromcontacts 15. Thus the circuit conditions in effect when the controlleris in its operated position are maintained under conditions of shock.Forces acting on the armature in the opposite direction and caused byshock similarly would be ineffective to disturb the circuit conditionsillustrated.

Fig. 10 is shown merely to illustrate a possible transfer arrangementsuitable for use in cases where the normal battery connection to a leadC is not so critically essential as to warrant safeguarding suchconnection under conditions of shock and where it is of prime importancethat the transfer operation result only from the normal operation of thecontroller and not from causes produced by shock. When the controller ofFig. 10 operates, armature 25 rotates in a clockwise direction causingthe battery connection to lead C to be opened at contacts BI and 82 andcompleting the battery connection to lead B by way of contacts 83 and 8dand their associated springs.

Should the controller illustrated in Fig. 10 be subjected to shock orimpact such as to cause the application of forces thereto in thedirection indicated by the broken line arrow, the armature would remainin its normal position due to its balanced condition and though contact83 would be closed due to the flexing of its associated spring, thecontact 84 would maintain the open condition of the lead B-due to theflexing of its associated spring away from the contact 84. Thus thetransfer of battery from lead C to lead B is prevented even though thebattery connection to lead B is interrupted.

While Figs. 5 to 10, inclusive, are intended to illustrate variousswitching functions capable of performance by aswitching deviceembodying the features of the invention, it is=to be understood thatthey do not constitute a showing of all the possible contactarrangements which are capable of being accommodated by such a switchingdevice. The schematic illustrations are intended to convey the factsthat the contacts may be of the break, make, or transfer types; that theswitching functions may be performed on a single pole or multiple polebasis; and that the stationary and spring supported contacts may be ofthe single or parallel variety, the lattertype serving as a. precautionagainst contact failure caused by dirt, dust or other extraneous matter.Obviously, the invention is equally applicable to controllers in whichthe contacts are closed, or opened in a definite sequence such as inswitching arrangement of the so-called make-beforebreak and"break-before-make types.

What is claimed is:

In a shock-proof switching device, a dynamically balanced armaturemounted for rotation about its transverse center axis, a contact springfixed to the upper surface of said armature, a contact spring fixed tothe lower surface of said armature, and a pair of circuit terminatingstationary contacts for each of said contact springs havingcorresponding contacts electrically interconnected, said pairs ofcontacts being so disposed relative to their corresponding contactsprings that each pair of stationary contacts'is bridged thereby whensaid armature'is in its normal position to effect duplicate parallelclosures of the circuit terminated by said stationary contacts, thearrangement of said springs on said armature relative to theircorresponding stationary contacts being such that the accidentalmovement of said springs, caused by shock, relative to their stationarycontacts precludes the simultaneous openings of the bridges effected bysaid springs.

2. In combination, an electric circuit having duplicate switching pointsand a switching device for controlling said circuit comprising a pair ofstationary contacts identifying each of said duplicate switching points,Wiring electrically interconnecting corresponding contacts of said pairsof stationary contacts, a dynamically balanced armature mounted forrotation about its center transverse axis, a pair of contact springseach bearing a pair of parallelly related contacts and mounted onopposite surfaces of said armature so as to extend radially fromopposite ends thereof, each said pair of parallelly related contactsnormally engaging a different pair of said stationary contacts wherebysaid circuit is rendered electrically continuous through two independentparallel paths, and means for rotating said armature to cause thesimultaneous disengagement of each of said pairs of parallelly relatedspring contacts from its corresponding pair of stationary contacts toeffect the simultaneous opening of said circuit at both said duplicateswitching points.

3. In combination, an electric circuit having duplicate switching pointswhose joint opening is required to effect a change in thenormalcondition of said circuit, and a switching device controlling saidcircuit comprising a pair of stationary contacts identifying each ofsaid duplicate switching points, a balanced armature mounted forrotation about its center transverse axis and normally assuming aposition of stable equilibrium in which it is unresponsive to shock, apair of bifurcated contact springs fixed to said armature each pair oftines thereof normally bridging the contacts of a different pair of saidstationary contacts, and wiring electrically connectingcorresponding'contacts of each pair of stationary contacts whereby thesaid circuit is rendered electrically continuous through two parallelpaths each including a pair of stationary contacts and the tines of thecorresponding bifurcated spring, said contact springs being susceptibleto movement relative to their stationary contacts and independently ofsaid armature when said device is subjected to shock and being sofixedly located on said armature and disposed relative to theirstationary contacts that they move in opposite directions relative totheir corresponding stationary contacts when said device is subjected toshock to thereby insure the electrical continuity of said circuitthrough one of said parallel paths, and in the same direction relativeto their corresponding stationary contacts when said armature is rotatedto thereby insure the opening of said circuit at both said duplicateswitching points.

4. In combination, an electric circuit having duplicate switching pointswhose joint closure, or opening, is required to effect a change in thenormal condition thereof, and a switching device for controlling saidcircuit comprising a pair of stationary contacts identifying each ofsaid duplicate switching points, a dynamically balanced armature mountedfor rotation about its center transverse axis, a birfurcated springinsulatively mounted on said armature having a pair of tines extendingradially therefrom in one direction each in engaged, or engageablerelation to a different contact of one of said pairs of stationarycontacts whereby the contacts of said pair of stationary contacts arenormally bridged, or bridgeable by said bifurcated spring, a secondbifurcated spring insulatively mounted on said armature having a pair oftines extending radially therefrom in the opposite direction each inengaged, or engageable relation to a different contact of the other ofsaid pairs of stationary contacts whereby the contacts of said otherpair of stationary contacts are normally bridged, or

vbridgeable by said second bifurcated spring, wiring electricallyinterconnecting corresponding contacts of each of said pairs ofstationary contacts, and means for causing the rotation of said armaturewhereby the tines of said contact springs are moved simultaneously into,or out of engagement withtheir corresponding stationary contacts tochange the condition of said circuit whichnormally prevails at saidduplicate switching points.

PAUL G. EDWARDS.

HAROLD W. HERRINGTON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 792,860 Sundh et al June 20, 19051,426,993 Kardaetz Aug.22, 1922 1,696,170 Leake Dec. 18, 1928 2,282,687Vigren et a1 May 12, 1942 2,344,809 Eaton Mar. 21, 1944 2,365,541Fountain Dec. 19, 1944

